A general concern in telecommunication networks of today is how to allocate resources, such as transmit power and frequency, in an appropriate manner. The resources are limited and as the number of links and subscribers continuously increases, the network complexity is increased, whereby more sophisticated solutions are needed. Typically, efficient resource utilization and reliable transmissions are aimed at.
Automatic Repeat reQuest (ARQ) and Hybrid Automatic Repeat reQuest (HARQ) are widely used in data transmission to keep the transmission quality. ARQ retransmits the data blocks when a NACK feedback is received to indicate an incorrect receiving. The receiver discards the failed blocks immediately. The principle of HARQ is instead to buffer the data blocks that were not received correctly and combine the buffered data with retransmissions. The soft combining procedure normally depends on which type of HARQ combining scheme that is used, e.g. Chase combining (HARQ-CC) or Incremental Redundancy (HARQ-IR) [1].
Existing solutions like the above-mentioned ARQ/HARQ mechanisms are associated with a number of problems. ARQ/HARQ tries to keep the transmission quality, but cannot guarantee successful transmissions. Even with the maximum number of retransmissions, the block may not be received correctly in a bad transmission environment. A higher limit of the maximum retransmission times will increase the transmission reliability, but will require larger buffer size and cause longer transmission delay.
To reach higher transmission efficiency, some studies have been done on HARQ/Adaptive Modulation and Coding (AMC) scheduling based on channel prediction [2]. The main concern of HARQ/AMC is to adapt or counteract the uncertainty of wireless channel variation and the most common measure is using the required average signal-to-noise ration as the metric. HARQ/AMC requires exhaustive simulation of all possible channel variations, which is a formidable task.
Accordingly, the handling of resources during transmission in conventional telecommunication systems is far from satisfactory and there is a considerable need for an improved resource allocation mechanism.